{"id":6539,"date":"2025-12-08T09:04:05","date_gmt":"2025-12-08T09:04:05","guid":{"rendered":"http:\/\/biodigestor.net\/?p=6539"},"modified":"2025-12-08T09:04:05","modified_gmt":"2025-12-08T09:04:05","slug":"results-are-expressed-as-positive-interactions-vs","status":"publish","type":"post","link":"https:\/\/biodigestor.net\/?p=6539","title":{"rendered":"\ufeffResults are expressed as % positive interactions vs"},"content":{"rendered":"

\ufeffResults are expressed as % positive interactions vs. antimicrobial mechanism requiring delivery of bacilli to a late endosomal compartment. Using macrophages expressing GFP-LC3 we observed the induction of autophagy specifically by a high intracellular weight ofM. tuberculosis. Bacilli were identified in LC3-positive compartments and LC3-positive compartments were confirmed to be acidified and LAMP1 positive. Thus, the antimicrobial effect of nave macrophages acting onM. tuberculosisin heavily-infected macrophages is usually contact-independent. Interleukin-1 provides an afferent signal that induces an as yet unidentified small molecule which promotes nitric oxide-dependent antimicrobial activity against bacilli in autolysosomes of heavily infected macrophages. This cooperative, innate antimicrobial interaction may limit the maximal growth rate ofM. tuberculosisprior to the expression of adaptive immunity in pulmonary tuberculosis. == Introduction == A role for apoptosis in innate defense againstMycobacterium tuberculosis(M.tb) was suggested by evidence that attenuatedM.tbH37Ra andM. bovisBCG induced tumor necrosis factor (TNF) stimulated apoptosis in infected macrophages, which was associated with a reduction in bacillary viability[1],[2]. In addition to the direct antimicrobial processes occurring in apoptotic macrophages, a previous study by Fratazzi et al.[3]demonstrated that this addition of nave macrophages to macrophages infected with an apoptosis-inducing strain ofM. aviumstrongly inhibited bacillary growth. This co-culture effect was observed when the infected cells were apoptotic, but not if they were made necrotic by sonication. The host-protective effects of apoptosis in tuberculosis (TB) is now an accepted paradigm but its biological relevance is usually uncertain since virulentM.tbinhibits the apoptotic death of infected macrophages[2]and uses these cells as a replication niche. Lee et al.[4]reported that virulentM.tbinduces an atypical, ultimately necrotic mode of macrophage cell death at threshold intracellular burden of 25 bacilli per macrophage. In the first several hours after high multiplicity of contamination (MOI) challenge, infected macrophages have apoptotic features of nuclear condensation and phosphatidylserine (PS) externalization without apoptotic Rabbit Polyclonal to GABBR2<\/a> vesicle formation. Adding nave macrophages during this pre-necrotic interval was shown to inhibitM.tbreplication, whereas adding nave macrophages at 24 h post-infection when the infected populace was necrotic had no antimicrobial effect. In the present study we investigated the mechanism responsible for inhibitingM.tbreplication in co-cultures of nave and infected macrophages, initially screening the hypothesis that this depended on phagocytosis of apoptotic bodies (efferocytosis) by the nave populace. Results did not support that hypothesis: confocal microscopy demonstrated incomplete engulfment of infected macrophages (frustrated efferocytosis) and the antimicrobial effect contributed by nave macrophages was found to be contact-independent. We Propyzamide show that nave macrophages are stimulated in an interleukin-1 receptor (IL-1R)-dependent manner to produce a soluble factor that acts back on heavily infected macrophages to restrictM.tbgrowth in a nitric oxide-dependent manner. This implies the delivery of bacilli to a late endosomal compartment, and in that regard we showed that a high intracellularM.tbload is sufficient to induce autophagy in macrophages. Our data reveal crosstalk between infected and uninfected macrophages that inhibitM.tbreplication, most likely by promoting antimicrobial processes in autolysosomes prior to the completion ofM.tb-induced necrosis. These interactions may serve to limit the maximal proliferative potential ofM.tbduring the early phase of pulmonary TB before the expression of adaptive immunity. == Results == == Cell contact is not required for co-culture antimycobacterial activity == Previous studies of macrophages infected withM. aviumorM.tbdemonstrated that co-culture with nave macrophages restricted mycobacterial growth, but only when the originally infected cells exhibited features of apoptosis[3],[4]. It was speculated in those reports that antimycobacterial activity might depend on uptake of bacilli by uninfected macrophages via efferocytosis of apoptotic host cells, but this was not formally tested. To investigate that question we first assessed whether efferocytosis occurs in co-cultures of nave cell line macrophages stained with Cholera toxin 488 andM.tbErdman-infected macrophages (MOI 50) stained with Cholera toxin 647. Under these conditions the infected populace is committed to death and externalizes PS but would not have progressed to necrosis, which is not widespread until 24 h post-infection. Samples were fixed at 4, 6, and 8 h after Propyzamide<\/a> co-culture and examined by confocal microscopy. Interactions between infected and uninfected macrophages consistent with early or attempted engulfment were evident at all time points.Determine 1Ashows pedestal formation and partial engulfment of whole infected cells at the synapse between these cell populations (white arrows). Total internalization of infected macrophages was not observed Propyzamide even after 24 h of.<\/p>\n","protected":false},"excerpt":{"rendered":"

\ufeffResults are expressed as % positive interactions vs. antimicrobial mechanism requiring delivery of bacilli to a late endosomal compartment. Using macrophages expressing GFP-LC3 we observed the induction of autophagy specifically by a high intracellular weight ofM. tuberculosis. Bacilli were identified in LC3-positive compartments and LC3-positive compartments were confirmed to be acidified and LAMP1 positive. Thus,… Continue reading \ufeffResults are expressed as % positive interactions vs<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4497],"tags":[],"class_list":["post-6539","post","type-post","status-publish","format-standard","hentry","category-calcium-ionophore","entry"],"_links":{"self":[{"href":"https:\/\/biodigestor.net\/index.php?rest_route=\/wp\/v2\/posts\/6539"}],"collection":[{"href":"https:\/\/biodigestor.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/biodigestor.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/biodigestor.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/biodigestor.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=6539"}],"version-history":[{"count":1,"href":"https:\/\/biodigestor.net\/index.php?rest_route=\/wp\/v2\/posts\/6539\/revisions"}],"predecessor-version":[{"id":6540,"href":"https:\/\/biodigestor.net\/index.php?rest_route=\/wp\/v2\/posts\/6539\/revisions\/6540"}],"wp:attachment":[{"href":"https:\/\/biodigestor.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6539"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/biodigestor.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6539"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/biodigestor.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6539"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}